The broad, long term objectives of this study are to (I) identify and characterize the growth factor-receptor systems through which the functions of corneal, immune, and other cells of the anterior segment of the eye are controlled during development, homeostasis, and wound healing; (II) understand at the molecular and cellular level, the factors that lead to corneal opacity, and its resolution, after injury, surgery or infecion; (III) explore the mechanism of epithelial basement membrane (EBM) regeneration after injury, including the role of corneal stromal cells in EBM regeneration, and the importance of the corneal EBM in modulating epithelial-stromal interactions in the cornea, including the development of myofibroblasts associated with stromal opacity. Photorefractive keratectomy (PRK) and irregular phototherapeutic keratectomy (PTK) are reproducible models of corneal stromal opacity that occurs after surgery, injury or infection. The Specific aims of this proposal are to test the hypotheses that 1) the full structural regeneration of the corneal EBM, including the lamina lucida and lamina densa, a) occurs over a period of several days after injury to the epithelium, EBM and stroma, b) depends on the contribution of critical EBM components from stromal cells, in addition to epithelial cells; 2) in corneas that develop stromal opacity after hih correction PRK, the epithelial basement membrane does not regenerate properly because myofibroblasts that are generated after injury do not produce, or correctly localize, basement membrane components required for EBM regeneration and persist as a barrier to block keratocyte/ corneal fibroblast contributions of critical components needed for EBM regeneration; 3) that cultured keratocytes, corneal fibroblasts and myofibroblasts (keratocyte-derived and bone marrow-derived) have differential expression of EBM components that contribute to the lamina lucida and lamina densa of the EBM; and 4) that a) bone marrow-derived cell precursors to myofibroblasts in the cornea are fibrocytes, b) that the proportion of myofibroblasts in a cornea with haze derived from bone marrow-derived precursors compared to myofibroblasts derived from keratocyte-derived precursors increases in proportion to the extent of stromal injury and c) regeneration of EBM entails cytokine- mediated epithelial-stromal interactions mediated by interleukin-1 that regulate the expression of EBM components by keratocytes.